Recurrent miscarriage is associated with a decline of decidual natural killer cells expressing killer cell immunoglobulin‐like receptors specific for human leukocyte antigen C

AIM: To investigate the relationship between natural killer (NK) cell phenotype and recurrent miscarriage (RM). METHODS: We studied killer cell immunoglobulin-like receptor (KIR) expression on decidual NK cells in women with RM. RESULTS: The expression of KIR2DL1/S1 on CD56(+) CD16(-) NK cells in the deciduas of these women was significantly lower than in that of control subjects (P = 0.026). There was a significant decline in the frequency of CD56(+) CD16(-) NK cells staining for KIR2DL1/S1 and KIR2DL2/S2/L3 throughout the first trimester in patients (P < 0.05). Furthermore, by stratification of the women in three groups according to gestational stage, it was found that KIR2DL1/S1 expressing NK cells were significantly decreased in all groups, especially around gestational days 50-70 (P = 0.010). CONCLUSION: This is the first report to demonstrate that RM is associated with a decline in the frequency of decidual NK cells expressing KIR specific for human leukocyte antigen (HLA)-C, and in which gestational stage was considered. The results suggest that KIR phenotype contributes to the pathogenesis of the disease, and that assessment of KIR may serve as a diagnostic tool.